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Sharks' 'aggressive' behavior isn't


© St. Petersburg Times,
published September 8, 2001

Question: Who knows the most about these sharks and their attacks on people? This is really something this summer.

Do veterinarians ever treat sharks in captivity for their health problems? What diseases do they get? I have heard they don't get cancer.

Why can't you do something to tame their aggressive tendencies lately?

Answer: Mote Marine Laboratory in Sarasota operates an independent, nonprofit research organization dedicated to excellence in marine and environmental sciences. Scientists at the lab are considered among the foremost specialists in shark biology, including their anatomy, physiology, pathology (diseases) and ecological habits within their marine environment.

Mote conducts field studies of shark nursery areas in the U.S. and Mexican Gulf of Mexico, the Gulf of California and other regions. It studies population dynamics such as the abundance of shark species in various locations (e.g. the areas where recent shark bites have occurred near Florida beaches). Shark food habits, feeding mechanisms and visual acuity are among other important issues explored at the lab.

This description barely touches the extensive nature of research and activities going on at Mote Marine Laboratory. For more information, you may make a personal visit to the lab; write Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236; or view the Web site,

In answer to your other questions: Historical and scientific data indicate that the number of shark attacks on people in Florida coastal waters is not statistically higher than in past years. These are not demonstrations of unusually aggressive behavior.

Sharks routinely swim in our nearby ocean waters and have done so for millions of years. They do this in search of food, usually marine life such as fish. If a human swimmer or surfer happens to be in the area and conditions are right (such as low visibility), sharks may mistake them as a source of food. However, the huge national media focus on these recent unfortunate biting episodes has distorted their magnitude out of proportion, making them appear to be much more frequent than they actually are.

Sharks are being hunted down, and their numbers are being reduced at an alarming rate. This is happening largely because the public imagination has been fired by many erroneous stories depicting the shark as a predator that seeks out human prey. This could eventually deplete a valuable resource before we understand enough about this animal and the benefits it could hold for mankind.

Veterinarians are involved with the health care of sharks in captivity and in the wild. They also work closely with marine biologists in various research projects exploring the nature of their reproductive activities and endocrine systems as well as disease processes. One current project involves determining the effects of pollution on the reproductive fertility of sharks in Tampa Bay.

Some of the common conditions for which sharks are treated in captivity include internal and external parasites as well as bacterial and fungal infections. Sharks are also affected by many of the same types of diseases that affect other animals, such as goiter, hepatitis, etc.

Although cancer has, on occasion, been diagnosed in sharks, it appears to be rare. One study at Mote determined that carcinogens (substances that cause cancer) have no affect on sharks and their relatives, skates and rays. Mote scientists are studying this phenomenon to help explain why. Learning about this could shed light on potential benefits to humans and other mammals.

Finally, one last point regarding sharks' "aggressive tendencies" should be made. What you are calling aggressive tendencies is merely normal behavior that sharks have exhibited since long before humans entered the marine environment. In fact, their behavior is rarely aggressive, a fact that can be confirmed by almost any diver who has seen them in their natural environment. The aggression in this case may be more by the media than the sharks.

-- Charles A. Manire, DVM, animal care manager, Mote Marine Laboratory, Sarasota

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Dr. Bruce Kaplan is a veterinarian editor/writer. Please send questions to Ask a Veterinarian, Pinellas Animal Foundation, P.O. Box 47771, St. Petersburg, FL 33743-7771. Because of the volume of mail, personal replies are not possible. Questions of general interest will be answered in this column.

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